Capacity control for compressors



Aug. 9, 1960 K. M. GERTEIS CAPACITY CONTROLIFOR COMPRESSORS Original Filed Feb: 26, 1954 5 Sheets-Sheet 1 FIG. I

FIG. 6

IN V EN TOR.

ATTORNEY.

KARL. M. GERTE IS Aug. 9, 1960 GERTEIS CAPACITY CONTROL FOR COMPRESSORS Original Filed Feb. 26, 1954 3 Sheets-Sheet 2 FIG. 2

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Aug. 9, 1960 Original Filed Feb. 26, 19 54 K. M. GERTEIS 2,948,293

CAPACITY CONTROL .FOR COMPRESSORS 3 Sheets-Sheet 3 FIG. 4

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FIG. 3-

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KARL M. GERTEIS BY WJLJ ATTORNEY.

'CAPACITY CONTROL FOR COMPRESSORS Karl M Gerteis, Syracuse,'N.Y., assignor to Carrier Corporatron, Syracuse, N.Y., a corporation of Delaware Original application Feb. 26, 1954, Ser. No. 412,793,

now Patent No. 2,836,345, dated May 27, 1958. Divrded and this application Aug. 1, 1957, Ser. No.

1 Claim. (Cl. 137-107) Patented Aug. 9, 1960 scribed. Therefore, it will be appreciated that the motor will not be subject to the loading due to the action of the loaded cylinders until the starting operation has reached a stage capable of operating under such a load.

Other objects and features of this invention will be apparent upon a consideration of the ensuing specification and drawings wherein:

Figure 1 is a diagrammatic view illustrating a compressor including the capacity control system of the present invention;

Figure 2 is a view partly in elevation and partly in section illustrating means for disposing the suction valve of a cylinder in an inoperative position;

' Figure 3 is a sectional View of the control valve; Figure 4 is a sectional view of the regulating valve,

: showing the improved safety feature forming the invention; Figure 5 is a view similar to Figure 4 showing the operating parts of the regulating valve in a different position; and

Figure 6 is a diagrammatic view illustrating the man net in which the individual elements of the improved element capable of unloading a cylinder of a compressor by holding the suction valve of the cylinder temporarily op'en. The system is generally similar to that disclosed in United States Letters Patent No. 2,626,099, issued January 20, 1953, in the name of Carlyle M. Ashley,v

and includes a control valve for selectively operating the various power elements and a regulating valve, operable in response to a change in load on the compressor, for the control valve.

The chief object of this invention is the provision .of acapacity control system of the type described which includes means for operating the system dependent upon a predetermined condition existing within the compressor. The capacity control system is preferably actuated by oil pressure in the lubrication system of the compressor and the means mentioned above includes an arrangement which prevents the system from operating unless the oil pressure in the lubrication system has reached a predetermined amount. This particularfeature also becomes important during the time in which thecompressor is started, and also in the event the i inadequate pressure in the lubrication system.

lubrication system fails to produce pressure of a predetermined value. The arrangement forming a feature of .this invention prevents the capacity control system from further operation by causing the cylinders equipped with unloaders to become unloaded thereby reducing the upon the refrigeration system as reflected by the pressure load on the 'machine. Another object of the invention is the provision of an improved control valve for use in the system which includes an unique construction preventing rapid cycling of. the cylinders in response to load variations. This condition occurs when, for example, the reduction in load is suflicient to cause a cylinder to unload but the reduced'output of thecompressor is insuflicient to meet th e'reduced load requirement. a a One. instance where a compressor capacity control system having a time delay feature, of the type tobe described, is particularly useful, occurs when the compressor motor must he started by applying the current thereto in step or stage fashion. Under these circumstances the current used to start the motor is delivered to the motor in successive increments to certain windihgs. -To' prevent the motor from stallingunder a load supplied by the fully loaded cylinders, the unloader ,ele-' ments 'are temporarily isolated from the lubrication sysn b aria of time del y. n erstate-2 a capacity control system are related.

7 Briefly, the capacity control system includes one or more cylinder unloading elements, depending on the number of cylinders present, in communication with a common control valve having a spring urged piston movable in a passage in such manner as to permit the application of oil pressure to certain of the unloader elements. Movement of the piston in the passage is dependent upon an unbalanced force between the spring and a source of oil, the pressure of which is under the influence of a regulating valve, which in turn is subject to, the load on the compressor as evidenced by the suctionpressure to which the compressor is subjected. The oil under the influence of the regulating valve is a part of the lubrication system of the compressor and one feature of the invention involves preventing the passage of this oil to the control valve until the pressure in the lubrication system reaches a predetermined minimum value, and also preventing any attempt to unload when the oil pressure to the unloader is insufficient to positively effect operation of the unloader. This permits a more efiicienti operation of, the valve for the reason that th oil, once, it enters the control valve, to act inopposiidngiio the spring, is not subject, tovariations due to f As' pointed out above, the operation of the control valve is'dependent in part upon the demand upon the compressor 'and causes the individual cylinders to load or unload in accordance therewith. Changes in the load inth'efsuction line, however, tend to be small in compa son with .the change in capacity of the compressor near r illustration, one of two operating cylinders is unloaded. -It will be appreciated that the capacity of the compressor may be. reduced by 50% at this point..

The compressor tendsto balance against the load so that theunloadedjcylinder. sgrapidly loaded again, resulting in an action known as cycling. Rapid cycling often causes undue wear on the. parts involved and should be avoided or at least minimized. To accomplish the elimr inatign. ofirap id cycling, this invention includes an im proved control valve, incorporating a lost motion feature which. necessitates a relatively large suction pressure change before the'capacity control system changes from.

unloading to loading or vice versa after operating through a pattern thatlincludes either successively loading or unread ing, whilepermitting a relatively small differential In other words, when the capacity control system.

to ccur. for the-purpose of functioning in the latter mam operates to change from loading to unloading or vice versa, a relatively large differential in suction pressure is necessary before the change occurs.

Referring to the attached drawings, there is illustrated in Figure l a compressor 2 having a plurality of cylinders 3 and a crankcase 4. Disposed within the crankcase 4 is oil sump 5" for the operating mechanism of the compressor including crankshaft 6, piston 7, and connecting rod 8, all of which are elements of a conventional compressor used for illustration in a refrigeration system which forms no essential part of the invention but which, it will be understood, are present to form an operable compressor. 7

It will be appreciated that efiicient operation of the compressor necessitates varying the output of the compressor in accordance with the demand made thereon. One convenient method of varying the output of the compressor involves equipping certain of the cylinders with an unloader element as of the type illustrated in Figure 2. The unloader mechanism disclosed is utilized to place the suction valve 14 of the cylinder 7 in inoperative position and includes a lifter sleeve 10 surrounding the cylinder and being provided with an outwardly extending flange ll. The sleeve is adapted to move in a reciprocatory manner about the outer surface of the element from a lower limit as indicated by band 12 embracing the cylinder.

Disposed radially about the flange 11 and in engagement with the upper surface thereof are a plurality of lifter pins 13 which operate to lift suction valve 14 from its seat in valve plate 15 in response to the upward movement of the sleeve 10. Loading springs 16 surround the lower portions of the pins 13 and serve to maintain the bottoms of the pins in engagement with the flange 1 1 on the sleeve 10.

Movement of the sleeve 10 is provided by a power element comprising a forked lever 17 having the end portions in engagement with the underside of flange 11 and which is pivoted at its other end to a vertical rod member '18. The latter member is secured at its other end to piston 19 which moves within casing 20 in response to oil pressure introduced therein through line 21 in the manner to be later described. Casing 20 is provided with a top plate 22, having lever support 22' integral therewith, and a bottom plate 23, having an opening 24 communicating with line 21. A spring member 25 encircles the vertical rod 18 and bears against the top member 22 of the casing and the piston 19 as shown in Figure 2 so as to normally urge the piston to its lowermost position within the casing. Opening 26 is provided in casing 20 and is designed to accommodate oil which may seep between the piston and the wall of the casing. Thus, it may be seen that the power unloading element is so constructed and arranged as to cause the lifting pins 13 to move the suction valve 14 from its seat when there is inadequate oil pressure to overcome the action of the spring 25, in the casing. When adequate oil pressure is supplied to the power element, piston 19 is forced upwardly against the action of the spring 25 pivoting lever 17 on pivot 22' thus permitting sleeve 10 to move downwardly and allowing springs 16 to move lifting pins 13 downward so that valves 14 assume their normal position under the influence of positioning springs 27.

In Figure 3, a control valve 28 is illustrated Which permits oil pressure to be introduced into the various power unloaders in a sequence depending upon the load imposed upon the compressor. Control valve 28 comprises a casing 29 having a first end member 30 and a. second end member 31. The casing 29 is provided with a cylindrical bore 32 extending therethrough which accommodates a movable piston 33 having a head 34 and a hollow elongated shank 35, having its unattachedend open, depending therefrom. Bore 32 is in communication with a socket 36 positioned within end member 30 and which is provided with a portion of reduced is a spring member 49 having the outer end thereof in,

diameter 37, constituting a spring seat. One end of a spring member 38 is positioned against seat 37 and the other end of the spring 38 is in engagement with the under side of the head 34 so as to normally urge piston 33 to the left of the control valve as viewed in Figure 3. Opening 38 serves to vent oil to the crankcase'when the piston moves to right, acting as an escape outlet. The piston 33 is also provided, on the shank portion proximate the unattached end, with an annular ring member 39 which in eltect forms a radial rojection about the shank. Mounted within the bore 32 so as to surround the shank 35 of piston 33 is a bobbin 40, having a first enlarged end portion 41 providing a sealing engagement with the sides of the casing which define bore 32, an intermediate portion 42 of reduced diameter and, an end portion 43, including a sealing surface 45', the exterior surface of which is formed by a series of alternately spaced grooves and ridges .or lands 44 and 45.

Casing 29'has further provided therein radial bores 46 extending from bore 32 through the side of the casing and through a boss 47' located on the externalsurface of the casing. A pin 48 projects through aligned openings 49' provided in the boss 47. Seated against pin 48 engagement with a spherical ball 51, the parts being so designed and constructed that the balls 51 are normally urged inwardly of the casing into engagement with the grooves 44 on bobbin 40. Also positioned in casing 29 is a radial opening 53 in communication with the supply line of the lubrication system. The casing 29 is further provided with a series of radial openings 52 through which oil from the lubrication system .of the compressor passes en route to the individual unloading elements mentioned above. Cover 31 has provided therein an opening 54 for the reception of lines 55 connected to the regulating valve in a manner to be more completely described.

Figure 4 illustrates a preferred form of a regulating valve 56 to be used in the capacity control system. The valve includes a first casing member 56 which includes a system of passageways which direct and guide oil from the lubrication systenrthrough the regulating valve and to the control valve in such a manner as to move piston 33 and bobbin 40 so that any or all of the openings 52 may a be supplied with oil pressure through line 53. The regu-' lating valve includes a second casing portion 57, one end of which contains an internally threaded socket which adapted to cooperate with an externally threaded extension 58 0f the casing 56' so as to form therewith chamber 59. Disposed within chamber 59 is a bellows 60 subjected on one side to suction pressure through inlet 61. The opposite side of bellows 60 is subjected to a predetermined force exerted by spring 62. The force exerted by spring 62 may be adjusted by means of stem 63 mounted within a threaded block 64 which is equipped with a cap 65. In addition, such side of the bellows is subject to atmospheric pressure. Mounted within socket 66 of casing56 is a needle valve 67 which is normally urged to the left of the valve as viewed in Figure 4 so as to close port 68 serving as one extremity of a passageway 69. The needle is urged to this position by action of spring 70. Acting in opposition to the spring 70, through push rods 71, is the bellows 60, under the influence of spring 62. The individual parts are so constructed and designed that the addition to or subtraction of suction pressure will vary the amount to which the needle valve obstructs the port 68;

When the conditions within the compressor, as evidenced by the suction pressure on the bellows member 60, are such that the needle valve completely closes the port 68 then the full pressure in the lubrication system is'employed to force oil through line 55 against head 34 of piston member 33, forcing the latter element against.

the action of spring 38 to the ,right, as viewed ,in .Fi Ie 3, in a manner to be later described. Under these cir cumstances, the parts are so designed and constructed thatoil pressure from the lubrication system entering the casing 29 through opening 53 passes through the various ports and passageways 52 to the unloader elements. However, one feature of my invention involves obstructing the passage of oil pressure to the control valve until the pressure in the lubrication system reaches a predetermined figure. To accomplish this, one preferable form of construction includes, in the casing 56 of the regulating valve, a cylindrical bore 72 having an opening which is closed by plug 73, and which has assembled for movement therein a piston '74, adapted to be urged toward plug 73 under the influence of a spring 75. The spring has one end abutting against the piston and the other end seated against the end of bore 72. The piston 74 isprovided with a diametral bore7 6, in which is positioned a coil spring 77 tending to force two ball bearings 78 into annular grooves 79 formed on the wall of the bore 72. The piston has the external surface thereof provided with a series of spaced grooves 80 and .lands 81 as well as an axial projection 81 and is so constructed that under the influence of the spring 75 the piston is projected across an opening 82 which is in communication with line 55.

The position of the piston 74, in the absence of oil pressure, in the lubrication system of a magnitude sufficient to overcome the action of the spring, is shown in Figure 5 wherein the axial projection is in engagement with the inner surface of plug '73, so as to form a chamber 73'.

.When the oilpressure in the lubrication system reaches a predetermined value, the action of the spring 75 is overcome and the piston is moved to the retracted position within bore 72 as shown in Figure 4. The bore 72 is in normal communication with the lubrication system of the compressor through line 83 which is connected to the main lubrication line 1. j

After 'the oil pressure in the lubrication system reaches alvalue suflicient to overcome the actionof spring 75 so as to force piston 74 to the'left of the bore as viewed in Figure 4, opening 82 is placed in communication with bore 72 and the opening 88, the function of which will be explained later, is blocked. The opening 82 permits oil to flow through passageway 69 to the port 68 and also into the chamber 87 which is in communication with line 55. The oil then flows through line 55 to the control valve where its action is as described above. When the piston 74 is in extended position (see Figure 5) opening 88 connects bore 72, with chamber 87 permitting line 89 to vent oil to the crankcase. Thus the opening 88 serves as an escape outlet for oil which may be trapped in the circuit between the control valve and the regulating valve. For illustration, assume that the oil pressure in the lubrication system has dropped to the extent that spring 75 forces piston 74 to its extended position, blocking opening 82. Under these circumstances, the piston 33 in control valve 29, under the influence of the spring 38, is forced to the left as shown in Figure 3, so that oil in chamber 32 is forced through line 55, chamber 87, passageway 88, and through line 89 to the crankcase.

In order to delay the operation of the needle valve 67 in the regulating valve, it may be desirable to include in the construction, a surge chamber of the type disclosed in co-pending application Serial No. 308,254, filed September 6, 1952, in the names of Lars Hanson et a1. As shown in Figure 6, the chamber 90 is formed in the end cover of the compressor and is provided with a cover 92 in the manner shown. A first opening 94 in the cover permits oil at crankcase pressure to be introduced into the chamber and a second opening 96 communicates with a line connecting the chamber and the regulating valve. Under this arrangement changes in the suction pressure in the compressor will be transmitted to the regulating valve, through the chamber which acts in the manner of a dampening agent, thereby delaying the transmittal.

In order to more adequately describe my invention, the operation'thereof will be explained. When the compressor is started, the power unloader elements, because of a lack of oil pressure, are arranged with the sleeve 10 in its uppermost position and pins 13 holding suction valves 14 in inoperative position so that the output of the unloaded cylinders is zero. In a relatively short period of time, the pump of the lubrication system, deriving its power from the compressor prime mover, forces oil through the lubrication system, which includes main line 1, from where it moves to line 83 and cylinder 72. Asdiscussed above, further movement of the oil in this direction is prevented by piston 74. Oil is also delivered from the main line 1 through line 53 to the control valve 28'. Dueto the absence of oil in line 55,.the piston 33, together with bobbin 40, are positioned within the control valve in such a manner as to prevent passage of the oil fromline 53 through any of the openings 52. The action of spring 38 moves the piston 33 to the left of the valve, as shown in Figure 3, and the annular ring 39 engages flange 41 of the bobbin, so that the flange 41 is positioned within the opening 32 between opening formed by the-line 53 and the closest opening 52.

After the oil pressure in the lubrication system has been built up to a pressure suflicient to overcome the action of spring 75, the piston 74 is moved to its retracted position, in the manner shown in Figure 4. This is accomplished by the oil in line 83 entering bore 72 through grooves 80, seeping past the lands 81 into chamber 73' where the pressure gradually builds up to a value suficient to'overcome the force of the spring 75. Oil

is also free to seep to the left of the opening 83 in bore 72; however, it is vented to the crankcase through opening 88 and line 89. Because of the presence of the'spring actuatedball bearings 78 and the grooves 79, the force necessary to project or retract the piston 74 over outlet 88 is abrupt and may be considered as snap-acting. This arrangement prevents any amount of oil, other than that under pressure suflicient to properly actuate the control. valve 28, from entering line 55. Oil is now free to flow through opening 82, to the control valve 28, via line 55. It is also free to flow to the port 68. The needle valve, at start-up, practically closes the port because of a high suction pressure condition prevailing so that the full pressure of the lubrication system will be exerted against the head 34 of piston 33, in opposition to the action of spring 38. The needle 67 is moved out of engagement with the port 68 in response to a reduction of the suction pressure within the suction manifold of the compressor and will move back to close the port 68 with a rise in suction pressure. The suction pressure is'indicative of the load being placed upon the refrigeration system so that the pressure exerted against the head 34 of piston 33 in control valve 82 is varied in response to the amount to which needle 67 restricts port 68. Thus it may be seen that the pressure of the oil in engagement with head 34 is subject to the action of the regulating valve. The strength of spring 38 may be varied in accordance with the pressure within the lubrication system so that the various ports of opening 52 are opened and closed in accordance with the pressure varying in line 55.

Assuming, during operation, the lubrication pressure drops below a minimum value, the piston 74 is immediately moved under the action of spring 75 to its extended position so as to block passageway 82 thereby causing. a substantial reduction in oil pressure in the line 55 so that piston 33 moves rapidly under the influence of spring 38 to close off the passageways 52 leading to the un-- loader elements. Thus, it may be appreciated that chattering of the suction valves in the individual cylinders due to inadequate oil pressure being maintained in the I unloader cylinders is obviated.

Another very important feature of the invention residesin the particular piston construction shown in Figures 4 and 5. The alternate grooves and lands on piston 74 prevent the piston'from beingforccdupward against the bore by permitting ,oil' to flow around th Piston so that any tendency for the piston to become lodged in'the cylinder is obviated.

Summarizing, it will be obvious that, by virtue of the construction disclosed herein, the successive loading of the cylinders will take place as the individual openings 52 of control valve 28 are placed in communication with opening 53 through the movement of the bobbin 40 and the head under which the oil, in pressure contact with,

piston33, is subjected. The action of spring 38' forces the piston 33 to the left of the control valve as received in Figure 3, however, bobbin 40 does not move to the left until the radial projection 39 engages it. Thus it will be noted that a pressure change of a magnitude sufficient to move the piston an amount equivalent to the distance from the right end of the bobbin to the radial projection 39 isv necessary before any of the openingsSZ are to be affected, while on the other hand the pressure change against piston 34 necessary to move the" piston in the direction currently moving is, relatively slight. The particular lost motion type of connection between the bobbin 40 and piston 337 permits the attainment of this feature.

It will be apparent that my invention may be incorporated in other construction without departing from the spirit and scope thereof. It will therefore be appreciated that the construction herein disclosed serves merely as an illustration of the invention and not a limitation thereof.

I claim:

Regulating valve mechanism for controlling fluid flow comprising a casing including means forming a first passageway having an inlet and an outlet for the passage of fluid through said casing, said casing including a cylinder having a section interposed between said inlet and said outlet so as to form a portion of the first passageway, means forming a second passageway communicating with the first passageway, condition responsive control means regulating flow through said second passageway thereby varying the: flow characteristics of the fluid flowing through said first passageway outlet, said casing being provided with a chamber having communication with said first passageway and with a second portion of said cylinder remote from the portion forming a part of the first passageway, means forming a second outlet serving as a cylinder drain, a piston disposed within said cylinder, said piston being provided with an axial projection and a slight clearance with respect to the cylinder wall and resilient biasing means urging the piston to a first operating position wherein said piston overlies the first passageway inlet with the axial projection in engagement with one end of the cylinder while establishing communication between the chamber and the second outlet serving as a drain through the second portion of the cylinder for the purpose of draining fluid from said mechanism, and a second operating position, attainable in response to an increase in pressure in the inlet to a predetermined force represented by the pressure of fluid in the space defined by the engagement of the axial projection and the end of the cylinder due to leakage about the piston, overlying the communication between the chamber and the second portion of the cylinder while establishing communication between the inlet and outlet of said first passageway so that the fluid flow from said first passageway outlet is responsive only to the action of the condition responsive control in said second passageway.

References Cited in the file of this patent UNITED STATES PATENTS 2,635,710 Tear Apr. 21, 1953 2,764,175 Mercier Sept. 25, 1956 2,771,898 Rotter Nov, 27, 1956 2,799,996 Van Meter July 23, 1957 

